Constantine I (DNB00)
CONSTANTINE I (d. 879), son of Kenneth Macalpine, king of Scotland or Alba, the country north of the Forth and Clyde, whose chief seat was Scone, succeeded his uncle Donald in 803. His reign was one of the first when the attacks of the Normans attained a formidable height, threatening the destruction of the Celtic and Saxon kingdoms. Two years after his accession Olaf the king of Dublin, wanted the country of the Picts, and occupied it from the Kalends of January to the feast of St. Patrick, i.e. 17 Marsh. According to the Pictish Chronicle, Olaf was slain by Constantine when on a raid in the following year, but the 'Annals of Ulster' relate that he destroyed Alrhyth (Dumbarton) after a four months' siege, in 870, and retired in 871 to Dublin with two hundred ships and a great bodjy of men, Anglo-Britons and Picts. After this he disappears from the Irish annals, so that his death may possibly have been antedated by some years in the account of the Pictish Chronicle. Ivar, another of the Norse Vikings of Dublin, who had fought along with Olaf, died about the same time, but Scotland was still exposed to incursions from other leaders of the same race. Thorstein the Red, a son of Olaf, by Audur, the wealthy daughter of Ketill Flatnose, attacked the northern districts, and, according to the 'Icelandic Landnamabok,' conquered 'Katanes and Suderland, Ross and Norway, and more than half Scotland.' But his kingdom, which, perhaps, was acquiesced in by Constantine, who had slight hold of the northern parts, was brief, and he was slain by the men of Alba by a stratagem or treachery in 875. In the South Halfdane the Danish leader who led the northern of the two bands (Guthrum, Alfred's opponent commanded the other), into which the formerly united host of that people was divided, ravaged the east coast of Britain, laid waste Northumbria, and destroyed the Picts (of Galloway?) and the people of Strathclyde.
Two years later another band of Danes, the Irish Dubhgall, or Black Strangers, having been driven from Ireland by the Fingall, or White Strangers, made a sudden descent on Scotland by way of the Clyde and, penetrating into the interior, defeated the Scots at Dollar, from which they passed to Inverdovat, in the parish of Forgan in Fife, where Constantine was slain (877). Tradition points to the long black cave, near Crail, as the scene of his death.
[Robertson's Scotland under her Early Kings; Skene's Celtic Scotland.]